Endoscopic probe

ABSTRACT

An endoscopic probe suitable for use as a TEE-probe, comprising a flexible tube having at one end a probe head which is provided with a phased array ultrasonic transducer with a number of elongated transducer elements which can be individually electrically controlled by cables connected to the individual elements and extending through a flexible tube in which the transducer is mounted in a cylindrical transducer housing, which is in a cavity in the probe head and is rotatable about a longitudinal axis extending at right angles to the longitudinal axis of the probe head, by means of a drive means interacting with the transducer housing while the elongated transducer elements are connected by flexible conductors to the cables extending through the flexible tube and in which a convex acoustic lens is mounted on the transducer and the peripheral edge of the lens interacts in a sealing manner with the edge of the cavity in the probe head and can rotate together with the transducer relative to the probe head.

The invention relates to an endoscopic probe, in particular suitable foruse as a TEE probe, comprising a flexible tube having at one end a probehead which is provided with ultrasonic transducer means of the phasedarray type with a transducer made up of a number of elongated transducerelements, which elements can be individually electrically controlled bymeans of cables connected to the individual elements and extendingthrough the flexible tube, the transducer being mounted in anessentially cylindrical transducer housing which is placed in a cavitywith an aperture in the probe head and is rotatable about a longitudinalaxis extending at right angles to the longitudinal axis of the probehead by means of drive means interacting with the transducer housingwhile the elongated transducer elements are connected by means offlexible conductors to the cables extending through the flexible tube.

An endoscopic probe is known from the article "An endoscopicmicromanipulator for multiplanar transesophageal imaging" by Roy WMartin et. al. in Ultrasound in Med & Biol., Vol 12, No 12, pp. 965-975,1986. The known probe has a probe head with a slightly flattened partcontaining an essentially flat transducer made up of a number ofindividual adjacent elongated elements of piezoelectric material whichcan be excited individually, and which together form a phased array. Byexciting the strip-type elements in a suitable sequence, it is possibleto obtain a beam which scans the environment to be examined and producesreflections in a plane lying at right angles to the elongated elements,as described in greater detail by J. C. Somer in "Echocardiography", N.Bom, published by Martinus Nijhof in The Hague, 1977. Rotating theflexible tube and thus the probe head, about the longitudinal axis meansthat the environment around the probe head can be scanned by anultrasonic beam. Pulling cables also extend through the flexible tube,by means of which said head can be pulled forwards or backwards.

In the medical world there is a need for an endoscopic probe with whichmore information can be obtained. In the past it was proposed that abiplane TEE probe should be used for this purpose. Such a probe head hastwo transducer arrays lying one after the other in the lengthwisedirection of the flexible tube and the head, each again composed ofadjacent elongated elements. The elements of one transducer extend atright angles relative to the elements of the other transducer. With thishead it is therefore possible to obtain two scanning beams which cancarry out a scanning movement in directions extending at right angles toeach other.

A disadvantage of this known probe is that the scanning beams originatein two different points. Another disadvantage is that the rigid head isrelatively long, which can lead to problems in practical use. Twoseparate transducer arrays with the same definition per array alsorequire twice the number of control cables, which all have to beconveyed through the flexible tube. However, the flexible tube haslittle or no pace for these.

In order to eliminate these problems, it was proposed in U.S. Pat. No.4,543,960 that the transducer array should be fitted in the probe headso that it is rotatable about an axis extending at right angles to theplane of the array. For this, a transducer housing, bearing thetransducer array and rotatable about a pin provided on the side of thetransducer housing facing away from the array, is fitted in a cavity inthe probe head. The elements of the transducer array are connected bymeans of conductors formed on two flexible printed circuit boards to thedifferent cores of one or more electrical cables extending through theflexible tube.

The flexible printed circuit boards lie coiled around the transducerhousing.

It is not indicated in U.S. Pat. No. 4,543,960 whether, and if so inwhat way, the cavity in which the transducer housing with the transduceris situated is sealed off relative to the environment. A good seal withas few seams and crevices as possible is, however, necessary from thepoint of view of hygiene if the probe is intended for repeated use.

The object of the invention is therefore to provide an endoscopic probewhich meets the abovementioned requirement, and more generally toprovide an endoscopic probe which is suitable for repeated use ondifferent patients, and by which the human body can he examinedinternally by echography in the optimum manner.

For this, according to the invention an endoscopic probe of theabove-described type is characterised in that a convex acoustic lens isfixed on the transducer said lens being provided in said aperture, andthe peripheral edge of the lens interacts in a sealing manner with theedge of the aperture in the probe head such that the cavity is sealed atthe level of the aperture by the lens and that the lens is rotatabletogether with the transducer relative to the probe head.

The invention will be described in greater detail below with referenceto the appended drawing of a number of examplary embodiments.

FIG. 1 shows schematically a cut-away top view of an examplaryembodiment of a probe head of a TEE probe according to the invention;

FIG. 2 shows schematically a cut-away side view of the probe head ofFIG. 1;

FIG. 3 shows schematically a top view of the probe head of FIG. 1, in adifferent working position;

FIG. 4 shows detail of the probe of FIG. 1 and FIG. 2;

FIG. 5 shows an example of a special printed circuit board which can beused in a probe according to the invention;

FIG. 6 shows a modification of the flexible printed circuit board ofFIG. 5;

FIG. 7 shows schematically a first example of an embodiment of a sealbetween a rotatable acoustic lens and the remainder of the probe head;

FIG. 8 shows schematically a variant of FIG. 7; and

FIGS. 9 to 11 show schematically a number of other examplary embodimentsof a lens which is rotatable relative to the remainder of the probehead.

FIGS. 1 to 3 show a TEE probe as an examplary embodiment of theinvention. A TEE (trans esophageal echocardiography) probe is a devicewhich can be used to examine the heart, or other parts of the body inthe region of theoesophagus, by ultrasonic radiation from the oesophagusthrough the oesophagus wall. The device shown comprises a probe head 1with a housing 2, which connects to a flexible end part 3 of a flexibletube which is notshown. Using Bowden cables 4, 5 extending through theflexible tube, the probe head can be bent forwards (as shown in FIG. 2)or backwards. This movement is made possible by the end part 3. Ifdesired, similar Bowden cables which permit a sideways swing of theprobe head can be present.

The housing 2 connects by means of a connecting piece 6 with roundcross-section to the end part 3 of the flexible tube, but itself has anessentially rectangular cross-section with rounded edges which widensout slightly to a holder 8 which is shut off at the free end by asemi-circular wall 7, and in which an ultrasonic transducer of thephased array type is placed. The holder 8 is provided with a circularaperture 9 in an essentially flat top wall. Situated in and behind theaperture is the transducer which, as can be seen in FIG. 2, comprises anessentially flat transducer 11 lying on a backing layer 10. Thetransducer 11 is made up of a number of adjacent, but separatestrip-type transducer elements which can be, for example, piezoelectricelements, and which in the situation shown in FIG. 1 extend parallel tothe longitudinal axis H of the probe head. The backing layer absorbsultrasonic vibrations which are radiated towards the interior of theprobe head and which, if not absorbed, would lead to disturbingreflections. The backing layer 10 is confined inside an electricallyinsulating frame 12 which can be made of, for example, a suitableplastic.

Above the array 11 is an acoustic lens 13, which will be described ingreater detail below. In a suitable manner phasedly exciting theindividual strip-type transducer elements makes it possible to obtain anultrasonic beam which can scan an area the shape of a sector of a circlein a plane at right angles to the strip-type elements. This technique,which is known per se, can therefore be used to scan the environment ofthe probe head with a swinging beam, but the swing can take place inonly one plane.

The lens 13, the transducer 11, the frame 12 and the backing layer 10are placed in a transducer housing 14 which is an essentiallycylindrical shape. The transducer housing is sealed at the level of theaperture 9 by the lens 13, and in the example shown also has a bottom 15which is supported on a pin 16 fitted in a bore in the wall of thehousing oppositethe aperture 9. The central axis of the pin coincideswith the central axisH2 of the transducer housing, and the centre pointof the circular opening lies on said central axis H2, so that thetransducer housing is rotatable about the pin.

In the examplary embodiment shown the transducer housing is rotatablefrom the rest position shown in FIG. 1 both clockwise and anticlockwisethroughapproximately 90 degrees. FIG. 3 shows the probe head with atransducer 11 rotated through 90 degrees. The total rotation range istherefore 180 degrees, which means that a spatial area the shape of thesector of a sphere can be scanned completely with one and the samedisc-type transducer made up of strips, without changing the position ofthe probe head itself.

In order to make the transducer housing 14 rotate in this example, abelt 17 is passed around the transducer housing, the two free ends 18,19 of which belt are connected to pulling cables 20, 21. The pullingcables are again in the form of Bowden cables, the outer cables of whichare shown at22, 23. The belt 17 can be a spring steel belt which 18connected at one point to the transducer housing 14, for example by asingle spot weld. Theconnection in the rest position is on or near thelongitudinal axis H1 of the probe head, as shown at 24 in FIGS. 1 and 4.

All this is shown again in FIG. 4. An interposed metal strip isindicated by 25 and is connected in a suitable manner to the transducerhousing. This prevents the pulling belt from slipping over thetransducer housing.

For the electrical connection between the transducer elements and theelectrical cables passed through the flexible tube, use is made of aflexible printed circuit board on which conductor tracks, connected atoneside to the individual transducer elements and at the other side tothe cores of the electric cables, are provided.

A number of cables are indicated by 30 to 33 in FIG. 1. The flexibleprinted circuit board is indicated by 34, 35. The flexible printedcircuitboard extends from a supporting plate 36 situated in the part ofthe probe head 1 connecting to the flexible tube and reaches into thetransducer housing 14. For this purpose, the transducer housing isprovided with a recess 37 extending through approximately 180 degreesalong the periphery and being the height of the width of the flexibleprinted circuit board. Fitted in the transducer housing 14 under thebacking layer are two pins 38, 39 which are fixed on the bottom 15and/or in the backing layer 10. A strip of the flexible printed circuitboard is passed around each of the pins 38, 39. Each strip extends in aloop under the backing layer towards connecting electrodes fitted on oneend of the strip-type transducer elements. The flexible printed circuitboards thus do not take up any space around the transducer housing.

In the examplary embodiment shown, the connecting electrodes for allstrip-type elements are on the front side of the probe head. It is,however, also possible, for example. to fit the electrodes for theeven-numbered elements on the front side and the electrodes for theodd-numbered elements on the opposite side of the transducer.

The pins 38, 39 are preferably placed in such a way that the flexibleprinted circuit boards extend essentially through the axis of rotationH2 of the transducer housing not only in the rest position shown in FIG.1, but also on rotation of the transducer housing. Rotation of thetransducerhousing 14 therefore does not lead to a change in the spacerequired for the flexible printed circuit boards.

The parts of the flexible printed circuit boards extending outside thetransducer housing change position only to a very small extent duringrotation of the transducer housing, as can be seen from a comparison ofFIGS. 1 and 3.

The pins 38, 39 can be positioned as shown on both sides of thelongitudinal axis H just past the centre line extending at right anglestothe longitudinal axis.

The supporting partition 36 in this example bears on both sides printedcircuit boards 43, 44 with conductor tracks to which the ends of thecables 30 to 33 are connected. The connecting point between theconductorsof the printed circuit boards 43, 44 and the conductors of theflexible printed circuit board is indicated at 45.

FIG. 5 shows schematically a flat blank of a flexible printed circuitboard60 which can be used in the device described. The printed circuitboard shown has two wing strips 34, 35 which together form anapproximately V-shaped flat blank. Each wing 34, 35 has an elongatedpart 60, 61 which has a first end 62, 63 for connection to the printedcircuit boards 43, 44.

Each wing also has a short transverse part 64, 65 which in the fittedstaterests against the frame 12 at the front side (in FIG. 1 or FIG. 2).The transverse parts each have an end strip 66, 67. The end strips ofthe two transverse parts are connected to each other at 68 and thus formthe connection between two wing strips. The end strips in the fittedstate arefolded over approximately at right angles and at the bottomside lie against the connecting electrodes of the transducer elements.The connecting electrodes can be, for example, gold-electrodes, and theconnection can be made with conducting adhesive.

It is pointed out that the width of the elongated parts of the wingstrips:of the flexible printed-circuit board described together with thethicknessresulted for the backing layer largely determines the minimumheight of theprobe head. According to a further development of the ideaof the invention, the elongated parts 60, 62 in the fitted state arefolded double about a fold line extending in the lengthwise direction.

An example of a flat blank for a flexible printed circuit board used forthis purpose is shown in FIG. 6. The conductor tracks extending in thelengthwise direction of the elongated parts 60, 61 of the wing strips34, 35 of the flexible printed circuit board are in each case dividedinto twogroups 70, 71 and 72, 73 lying on both sides of a fold line 74,75. The height required for the flexible printed circuit board isthereby greatly reduced.

When a flexible printed circuit board with double-folded elongated partsofthe wing strips is used, if one or more printed circuit boards 43, 44are again used as the connecting elements between the cables 30 to 33and the flexible printed circuit board, the printed circuit board 43and/or 44 canbe provided with conductors on both sides. In this caseeach side of a printed circuit board 43 or 44 can, for example,correspond to one of the parts 70 to 73.

In principle, two (or more) individual flexible printed circuit boardscould also be used. The use of a single printed circuit board gives theadvantage that the position of the tracks, in particular in the endstrips, is determined accurately. With the correct selection of thecentre-to-centre distance of the tracks these can also be placedaccurately in line with the gold electrodes of the transducer elementsandafter correct positioning of a printed circuit board shifting of anysecondprinted circuit board cannot take place.

FIG. 7 shows schematically in longitudinal section a first example of anembodiment of an acoustic lens 80 serving as a sealing cap for thecavity in the probe head. The lens 80 is a convex lens which can be madeof, for example, silicone rubber of the RTV-J type. The lens shown has aconvex central part which is fixed on the rotatable transducer and acylindrical downgoing outer wall 81 which lies in a close fit in theaperture 9 in theprobe head. A sealing means is provided between thewall of the aperture shown comprises a peripheral groove 82 filled witha friction-reducing agent such as grease. The groove in this example isformed in the wall of the aperture 9, but could also be fitted in theouter wall of the lens, asshown at 83 in FIG. 8.

In the example of FIG. 8 the housing 14 is also provided with an annularperipheral edge 84 which lies in a close fit, but rotatably against thewall of the aperture 9 and promotes an accurate support and positioningofthe lens in the radial direction. The cylindrical wall 81 of the lensconnects in the axial direction, and through use of a shoulder 85 alsoin the radial direction, in a positive fit to the peripheral edge 84 ofthe housing 14. A suitable screening foil, for example of aluminiumcapton (polyimide) can be provided between the transducer 11 and theconvex lens.

FIG. 9 shows another example of an embodiment in which a convex lens 80,lying with a radial shoulder 87 on a flat top edge 88 of the probe headsurrounding the aperture 9, is again used. The lens also has acylindricaledge 89 which falls into the aperture 9. A ring 90 is placedover the radial shoulder 87, said ring being firmly fixed to the flattop edge 88 of the probe head and having an undercut filled with greasewhich accommodates the radial shoulder. The outer edge of the ring 90 isrounded, as indicated at 91. The ring 90 can be glued on the flat topedge. The housing 14 again has a part 84 which lies radially against thewall of the cavity in the probe head.

In the examplary embodiment shown in FIG. 10, the convex lens 80 isprovided with a peripheral lip 92. The lip rests slightly resilientlyagainst the top edge of the probe head. An axial groove 93 is fitted inthe bottom side of the lens, radially slightly inwards from the lip. Aring 94 of hard material, for example glass ceramic material such asMACOR, is fixed in the groove 93, for example by means of adhesive Thering can turn with little friction over the material of the probe head.InFIG. 10 the ring lies on the top edge 88 of the probe head, but thering can also extend in a groove along the edge of the cavity, as shownin FIG.11 at 95.

In the example shown, the ring is also glued to the adjacent part of thehousing 14.

In the cavity below the lip of the concave lens there is again grease,which has both a lubricating and a sealing effect.

It is pointed out that, after the above, various modifications areobvious for the expert. For example, instead of the belt 17 a circularpulling cable, provided with a nipple falling into a cavity of thetransducer housing, can be used.

As an alternative, the belt 17 could be replaced by yet anothertransmission mechanism such as a toothed rack which can be shifted by apulling cable in the lengthwise direction, and which engages on atoothed wheel coupled directly or indirectly to the transducer housingIn that case it would be possible to make do with one pulling cable.Springs whichpress the transducer housing back to a predetermined restposition can alsobe used.

Instead of a single flexible printed circuit board, as already stated,two or more flexible printed circuit boards or one or more bunches ofwires connected between the connectors 40, 41 and to the cables 30 to 33could be used.

The belt 17 can also be made narrower and is preferably slightlyrecessed in a groove in the transducer housing.

The transducer, which in the example shown is essentially flat andhexagonal, can also be, for example, round or rectangular and slightlyconvex or even concave.

It is also pointed out that the probe described can also in principle beused for examination through body cavities other than the oesophagus.

These and similar modifications are considered to fall within the scopeof the invention.

We claim:
 1. An endoscopic probe particularly suitable for use as a TEEprobe, comprising a flexible tube having at one end a probe heatcomprising an ultrasonic transducer means of the phased array typeincluding a number of elongated transducer elements individuallyelectrically controlled by cables connected to said individualcontrolled transducer elements extending through said flexible tube,said ultrasonic transducer means being mounted in an essentiallycylindrical transducer housing placed in a cavity in said probe head androtatable about a longitudinal axis of said probe head by drive meansinteracting with said transducer housing said elongated transducerelements being connected by flexible conductors to said cables extendingthrough said flexible tube, a convex acoustic lens is fixed on saidultrasonic transducer means with a peripheral edge of said lensinteracting in a sealing manner with an edge of said cavity in saidprobe head, said convex acoustic lens rotatable together with saidultrasonic transducer means relative to said probe head.
 2. Theendoscopic probe according to claim 1 wherein said acoustic convex lenshas a cylindrical peripheral portion closely fitted but rotatably withinsaid cavity, and wherein a grease-filled groove is provided in an outerwall of said cylindrical peripheral portion of said acoustic convexlens.
 3. The endoscopic probe according to claim 1 wherein said acousticconvex lens has a cylindrical peripheral portion closely fitted, butrotatably within said cavity, and wherein a grease-filled groove isprovided in an inner wall of said cavity at a level of said cylindricalperipheral portion.
 4. The endoscopic probe according to claim 2 or 3wherein said cylindrical peripheral portion connects axially to a topedge of said transducer housing.
 5. The endoscopic probe according toclaim 4 wherein said top edge of said transducer housing and saidcylindrical peripheral portion have complementary connector shoulders.6. The endoscopic probe according to claim 1 wherein said acousticconvex lens comprises along an outer periphery thereof a radial shoulderhaving a flat bottom face lying on a flat part of a top edge of saidprobe head enclosing said cavity, and wherein said radial shoulder isconfined under a ring firmly fixed on said top edge of said probe head,said ring having an inside undercut falling over said shoulder andfilled with grease.
 7. The endoscopic probe according to claim 6 whereinsaid acoustic convex lens has an axial shoulder just falling inside saidcavity.
 8. The endoscopic probe according to claim 1 wherein saidacoustic convex lens comprises at a bottom side near said cylindricalperipheral edge an axial groove in which a ring is fixed in a closelyfitting manner, said ring interacting in a sealing manner with said edgeof said cavity.
 9. The endoscopic probe according to claim 8 whereinsaid acoustic convex lens has a peripheral lip lying radially outsidesaid ring and rests slightly resiliently against said top edge of saidprobe head a chamber formed between said cylindrical peripheral edge,said ring and said top edge of said probe head being fitted with grease.10. The endoscopic probe according to claim 8 or 9 wherein said ring isof a glass ceramic material.
 11. The endoscopic probe according toclaims 8 or 9 wherein said ring is partly disposed into a recess in saidtop edge of said probe head.
 12. The endoscopic probe according toclaims 1, 2 or 3 wherein said flexible conductors are tracks formed on aflexible printed circuit board extending through an aperture into saidtransducer housing positioned in a loop shape in said transducer housingtowards said connecting electrodes of transducer elements.
 13. Theendoscopic probe according to claim 12 wherein said flexible printedcircuit board extends with a part lying between said cables and saidloop shape proximate said longitudinal axis of said transducer housingand wherein said aperture in said transducer housing forms an angle orarc of essentially 180°.
 14. The endoscopic probe according to claim 12or 13, wherein said flexible printed circuit board is passed round a pinfitted in said transducer housing.
 15. The endoscopic probe according toclaim 14 wherein said flexible printed circuit board is attached betweentwo pins fitted in said transducer housing, said pin extendingessentially parallel to said longitudinal axis of said transducerhousing and, when viewed from a part of said flexible printed circuitboard connected to said cables, are fitted just past said longitudinalaxis of said transducer, and in a rest position of said transducerhousing are situated on both sides of said longitudinal axis of saidprobe head.
 16. The endoscopic probe according to claim 12 or 13 whereinsaid transducer housing has a backing layer disposed inside aninsulating frame on which said transducer means is positioned.
 17. Theendoscopic probe according to claim 16 wherein said flexible printedcircuit board is positioned under said backing layer in said transducerhousing.
 18. The endoscopic probe according to claims 12 or 13 wherein aflexible printed circuit board in opened-out form is approximatelyV-shaped with two wing strips, each said wing strip having an elongatedpart and a short transverse part and connected to each other at a pointof transverse sections, each transverse section having an end strip onwhich said conductors terminate and where said conductors are connectedto said individual transducer elements.
 19. The endoscopic probeaccording to claim 18 wherein elongated sections of said wing stripshave at least two groups of conductor tacks lying on both sides of afold line extending in a lengthwise direction of said wing strips, andwherein each wing strip is folded double along said fold line.